Hydraulic valve with leakage control

ABSTRACT

A hydraulic valve of the spool type with means to trap hydraulic fluid which tends to leak between the spool and the bore of the valve in which it slides and to bypass said fluid to atmosphere or a tank in order to prevent it from flowing past the spool to actuate a hydraulic motor causing it to move or creep when it should be at rest.

United States Patent [1 1 Bantz [54] HYDRAULIC VALVE WITH LEAKAGECONTROL [75] Inventor: Clarence W. Bantz, Aurora, 111. [73] Assignee:Caterpillar Tractor 00., Peoria, 111.

[22] Filed: Sept. 2, 1971 [211 Appl. No.: 177,496

Related U.S. Application Data [63] Continuation of ser. No. 873,172,Nov. 3, 1969,

[ 1 Jan. 2, 1973 Primary Examiner-M. Cary Nelson AssistantExaminerRichard Gerard Attorney-Fryer, Tjensvold, Feix, Phillips &Lempio [5 7] ABSTRACT abandoned' A hydraulic valve of the spool typewith means to trap hydraulic fluid which tends to leak between the spool[52] U.S. Cl. .137/312, 137/517, l37/625.69 d the bore of the valve inwhich it Slides and to Int. ..Fl6k said to atmosphere or a tank in orderto Field 01 Search .69; 25 /3 4 prevent it from flowing past the spoolto actuate a hydraulic motor causing it to move or creep when it shouldbe at rest.

7 Claims, 2 Drawing Figures 14 1G 18 IO Z ,28 I as, g \x l o 2o 22 38HYDRAULIC VALVE WITH LEAKAGE CONTROL This is a continuation, of Ser. No.873,172, filed Nov. 3, 1969 and since abandoned.

Hydraulic systems on some machines now employ pressures as high as 5,000psi and it is difficult to contain hydraulic fluid at such pressureswith aspool type valve which is used extensively in such systems. It isfound that despite very close machining tolerances, some leakagepersists and causes a build-up of pressure in a hydraulic motor employedfor actuating or adjusting a machine component so that the componentwill move slowly or creep even though the valve is in its closedposition.

The present invention overcomes this difficulty by providing a spoolvalve in which leakage tending to pass a spool in its closed position istrapped and bled away from the valve before it enters the lines leadingto the hydraulic motor. Check valve means are provided in the passagethrough which the leaking fluid is bled and the check valves areautomatically closed when the spool valve is opened for the purpose ofdirecting pressure to a machine component to be actuated.

The invention is more fully disclosed in the following specificationwherein reference is made to the accompanying drawing.

In the drawing:

FIG. 1 is a schematic view in section of a spool valve embodying thepresent invention and FIG. 2 is a enlarged fragmentary section of a partof the valve shown in FIG. 1.

In the drawing, the valve is shown as having a body suitably bored forthe reception of a spool 12 which is slidably mounted in the bore.Actuating linkage is connected to the extending end of the spool in aconventional manner.

In the position in which the spool is illustrated, fluid under pressureentering through a port 14 is prevented from flowing out either of ports16 or 18 by lands 20 and 22 respectively of the spool. For purpose ofthis description, the ports 16 and 18 may be considered as connectedwith opposite ends of a motor such as a hydraulic jack so that when oneport is opened to admit fluid to one end of the jack, the other portwill be opened for return of fluid to tank from the opposite end. Whenthe spool is moved toward the right as shown in FIG. 1, land 22 admitsfluid under pressure from port 14 to port 18 communicating with one endof the jack cylinder. At the same time land 20 uncovers port 16 forreturn of fluid from the opposite end of the cylinder. The returnedfluid enters a passage 24 and is returned through a port 26 to a tankillustrated at 28'. Upon adjustment of the spool in the oppositedirection or toward the left, pressure is communicated through port 16to one end of the jack cylinder and returned from the opposite endthrough port 18 into the other end of passage 24 for discharge throughport 26.

If with the valve in its closed position, as shown in FIG. 1, fluidleaks past either of the lands 20 or 22, it will increase pressure atthe corresponding end of the jack cylinder imparting motion thereto andmoving or creeping of the component actuated thereby.

The present invention provides annular chambers 28, one of which isdisposed in the wall of the valve bore intermediate the inlet port 14and each of the ports 16 or 18 which communicate with the motor. Leakagefluid is intercepted by these annular chambers and communicated to thedischarge, passage 24 by means best illustrated in FIG. 2. In thisfigure, a

threaded plug 30 is contained in a passage which extends between themain valve bore and the discharge 5 passage 24. This plug contains acheck valve which includes a ball 32 urged toward an open position by aspring 34 which seats against an orificed spring seat 36 pressed intothe plug 30. The ball is urged into contact with a piston 38 slidable inthe bore above the ball and having a small orifice 40 through whichleaking fluid is discharged. Plugs 42 in the main valve housing areshown in FIG. 1 for closing openings through which the check valve andcylinder means may be inserted and removed.

In operation, any small quantity of hydraulic fluid tending to leak pastthe lands 20 or 22 will be bled through the orifice 40 of the piston 38and through the open check valve. During operation of the spool valvefor directing high pressure fluid to either of the outlets 16 or 18, thecorresponding leakage port is uncovered and, since the pressure andvolume of fluid is too great to pass through the small orifice 40, thepiston 38 moves downwardly forcing the ball 32 onto its seat againstpressure of the spring 34. Consequently, with the valve spool open, theleakage passage is closed.

What is claimed is:

1. In a spool valve having a bore and spaced inlet and outlet portscommunicating with said bore, a spool reciprocable in said bore andhaving land means forming a closure between the inlet and outlet portswhen the valve is closed, the improvement which comprises: means toprevent leakage of fluid under pressure to said outlet ports when thevalve is closed including drain passage means communicating with saidbore intermediate said inlet and outlet ports for directing leaked fluidto a low pressure area, and check valve means in said drain passagemeans, said check valve means being responsive to pressure at the areaof communication of said drain passage means with said bore to closesaid drain passage means when said valve is open and open said drainpassage means when said valve is closed.

2. The invention of claim 1 wherein said check valve means includes avalve element which is biased to an open position by spring means, andpiston means reciprocably mounted in said drain passage means and havinga port therethrough to permit escape of leaking fluid, said port beingdimensioned so as to be too small to pass full fluid flow when the valveis open, and said piston being subject to said fullflow and arranged toengage and close the valve element when the valve is open and the pistonis subjected to such flow.

3. The invention of claim 1 wherein said spaced inlet and outlet portscomprise an inlet port and a pair of outlet ports located on oppositesides of said inlet port, said land means comprising a pair of lands onsaid spool each one of said lands operating to close one of said outletports, and wherein said drain passage means comprise a pair of drainpassages, each one of said drain passages communicating with said boreand having check valve means in each drain passage.

4. The invention of claim 3 further including annular chamber means inthe wall of said bore to entrap fluid cooperating with each drainpassage so as to entrap leaked fluid around the circumference of thebore.

5. The invention of claim 1 wherein said drain passage means comprise adrain passage and wherein said check valve means comprises a valveelement in the form of a ball adapted to sealingly close against a seatand which is urged to the open position by a spring, and furtherincluding a piston reciprocably mounted in said drain passage and havingmeans therein for passing leaked fluid when the valve is closed, saidmeans in said piston operating to not pass the full flow of fluid whensaid valve is open whereby said piston is shifted by the pressure ofsaid full fluid flow to motivate and thereby close said valve elementagainst said seat.

6. The invention of claim 5 wherein said means in said piston comprise aport extending therethrough.

7. ln a spool valve having a bore with spaced inlet and outlet passagescommunicating therewith, a spool reciprocable in the bore and having aland forming a closure between the inlet and outlet passages when thevalve is closed, the improvement which comprises means to preventleakage of fluid under pressure to the outlet passage when the valve isclosed including an annular chamber in the wall of the bore between theinlet and outlet passages to entrap fluid before it enters the outletpassage, a drain passage to direct such fluid to a low pressure area,and check valve means which is responsive to inlet pressure within theannular chamber to close said drain passage when said valve is open andopen said drain passage when said valve is closed.

1. In a spool valve having a bore and spaced inlet and outlet portscommunicating with said bore, a spool reciprocable in said bore andhaving land means forming a closure between the inlet and outlet portswhen the valve is closed, the improvement which comprises: means toprevent leakage of fluid under pressure to said outlet ports when thevalve is closed including drain passage means communicating with saidbore intermediate said inlet and outlet ports for directing leaked fluidto a low pressure area, and check valve means in said drain passagemeans, said check valve means being responsive to pressure at the areaof communication of said drain passage means with said bore to closesaid drain passage means when said valve is open and open said drainpassage means when said valve is closed.
 2. The invention of claim 1wherein said check valve means includes a valve element which is biasedto an open position by spring means, and piston means reciprocablymounted in said drain passage means and having a port therethrough topermit escape of leaking fluid, said port being dimensioned so as to betoo small to pass full fluid flow when the valve is open, and saidpiston being subject to said full flow and arranged to engage and closethe valve element when the valve is open and the piston is subjected tosuch flow.
 3. The invention of claim 1 wherein said spaced inlet andoutlet ports comprise an inlet port and a pair of outlet ports locatedon opposite sides of said inlet port, said land means comprising a pairof lands on said spool each one of said lands operating to close one ofsaid outlet ports, and wherein said drain passage means comprise a pairof drain passages, each one of said drain passages communicating withsaid bore and having check valve means in each drain passage.
 4. Theinvention of claim 3 further including annular chamber means in the wallof said bore to entrap fluid cooperating with each drain passage so asto entrap leaked fluid around the circumference of the bore.
 5. Theinvention of claim 1 wherein said drain passage means comprise a drainpassage and wherein said check valve means comprises a valve element inthe form of a ball adapted to sealingly close against a seat and whichis urged to the open position by a spring, and further including apiston reciprocably mounted in said drain passage and having meanstherein for passing leaked fluid when the valve is closed, said means insaid piston operating to not pass the full flow of fluid when said valveis open whereby said piston is shifted by the pressure of said fullfluid flow to motivate and thereby close said valve element against saidseat.
 6. The invention of claim 5 wherein said means in said pistoncomprise a port extending therethrough.
 7. In a spool valve having abore with spaced inlet and outlet passages communicating therewith, aspool reciprocable in the bore and having a land forming a closurebetween the inlet and outlet passages when the valve is closed, theimprovement which comprises means to prevent leakage of fluid underpressure to the outlet passage when the valve is closed including anannular chamber in the wall of the bore between the inlet and outletpassages to entrap fluid before it enters the outlet passage, a drainpassage to direct such fluid to a low pressure area, and check valvemeans which is responsive to inlet pressure within the annular chamberto close said drain passage when said valve is open and open said drainpassage when said valve is closed.